Production of olefinic hydrocarbons



United States Patent Oflice 3,531,387 PRODUCTION OF OLEFINIC HYDROCARBONS Henryk A. Cyba and James J. Louvar, Evanston, Ill., as-

signors to Universal Oil Products Company, Des Plaines, Ill., a corporation of Delaware No Drawing. Filed Oct. 27, 1967, Ser. No. 678,504 Int. Cl. C07c 11/02 US. Cl. 20472 10 Claims ABSTRACT OF THE DISCLOSURE Olefinic hydrocarbons are prepared from paraffinic type carboxylic acids by subjecting said carboxylic acids to electrolysis in an electrolytic cell in the presence of certain metal salts, a specific example being the electrolysis of caprylic acid in the presence of cupric acetate to form l-heptene.

This invention relates to a process for the preparation of olefinic hydrocarbons and particularly a-olefinic hydrocarbons by subjecting a paraffinic type carboxylic acid to electrolysis in the presence of certain catalytic compositions of matter whereby the carboxylic acids will be subjected to oxidation to form an olefinic hydrocarbon. Specifically speaking, the invention is concerned with a process for obtaining a-olefins. These wolefins are finding a wide variety of uses in the chemical field. For example, l-butene which may be obtained from valeric acid by the process hereinafter set forth in greater detail may be used as an intermediate in the preparation of polymers, and particularly a dimer, which will possess a high octane number, and therefore will be a valuable component of gaoline. Likewise, a relatively longer chain u-olefin such as l-hexadecene will be useful as an alkylating agent in the preparation of detergents. When utilizing l-hexadecene or other a-olefins which contain from 12 to about 17 or 18 carbon atoms as alkylating agents in the alkylation of benzene, thereafter sulfonating the resultant alkyl aromatic hydrocarbon and obtaining the sodium salt by neutralization, it is possible to obtain detergent compounds which are biodegradable in nature. This is an important characteristic of detergents which are now being prepared inasmuch as a problem of pollution has arisen by utilizing detergents or surface active agents which are non-biodegradable in nature. This problem of pollution is apparent from large amounts of foam and suds which are prevalent in many rivers, streams or other sources of water which are needed to fulfill the requirements of many cities and towns adjacent to these water sources. Heretofore, detergents which contain long chain alkyl substituents have utilized, as alkylating agents, compounds which are highly branched in configuration. This branched chain configuration does not render the detergents biodegradable, and therefore the molecule will remain after use and thus contribute to the build-up of the aforementioned foam and suds. However, by utilizing an alkyl substituent which is straight chain in nature, the micro organisms which attack the molecule will be able to destroy said molecules after use thereof and thus prevent the formation of long-lasting foams. This type of detergent is said to be biodegradable. Therefore, as is readily apparent, the need of a-olefins in many phases of chemistry as a required substituent is increasing.

It is therefore an object of this invention to provide a process for preparing olefinic hydrocarbons.

A further object of this invention is to provide a process for preparing OL-OlBfiI'lS from parafiinic type carboxylic acids by subjecting said acid to an electrolysis process in the presence of certain catalytic compositions of matter.

In one aspect an embodiment of this invention resides in a process for the preparation of an olefinic hydrocar- 3,531,387 Patented Sept. 29, 1970 bon which comprises subjecting a carboxylic acid to electrolysis in an aqueous alkali-organic solvent medium in the presence of a metal salt which is capable of free radical oxidation, and recovering the resultant olefinic hydrocarbon.

A specific embodiment of this invention is found in a process for preparing an olefinic hydrocarbon by subjecting caprylic acid to electrolysis in an aqueous alkaliorganic solvent medium in the presence of cupric acetate at a temperature in the range of ambient to about 200 C. and at a pressure in the range of from about atmospheric to about atmospheres, and recovering the resultant l-heptene.

Other objects and embodiments will be found in the following further detailed description of the present invention.

As hereinbefore set forth the present invention is concerned with a process for the production of olefinic hydrocarbons, and particularly a-olefinic hydrocarbons, by subjecting a parafiinic type carboxylic acid to electrolysis in the presence of certain catalytic compositions of matter. The catalytic compositions of matter which are utilized to effect the oxidation of primary free radicals to a-olefins comprise salts of copper which are soluble in an aqueous alkali-organic solvent medium. Particularly preferred salts are those in which the copper is in a valence state of +2 and will include such soluble organic copper salts as cupric acetate, cupric formate, cupric butyrate, cupric pentanoate, cupric hexanoate, cupric heptanoate, cupric octanoate, cupric benzoate, cupric naphthoate, cupric lactate, cupric salicylate, etc.; inorganic copper salts such as cupric dichromate, cupric selenate, cupric molybdate, cupric tungstate, etc. organic complexes such as copper acetylacetonate, diamino copper acetate, tetraamino copper acetate, the copper salt of diethylenediamine tetraacetic acid, etc. In the preferred embodiment of the invention, the oxidation catalyst will be used in a range of from about 0.02 to about 0.03 molar concentration. However, it is also contemplated within the scope of this invention that lower or higher concentrations of the catalyst may also be used, although not necessarily with equivalent results.

The paraflinic type carboxylic acids which are subjected to electrolysis to form the desired tat-olefinic hydrocarbons comprise those which contain at least 3 carbon atoms in a straight chain and may contain from 3 up to about 50 carbon atoms in the acid molecule. The latter acids, namely, those which contain carbon atoms ranging from about 25 to about 50 carbon atoms are those which comprise substituted polymeric acids. The preferred carboxylic acids which are treated according to the process of this invention include those which contain from 3 to 22 carbon atoms in the chain as hereinbefore set forth, the only criteria which the paraffinic type carboxylic acid must have is that it contain at least 3 carbon atoms in a straight chain. Thereafter the chain may contain other substitutents, said substituents including alkyl, alkoxy, cycloalkyl, N-dialkylamino or phenyl radicals. It is preferred that these substituents are at least two carbon atoms distant from the carboxylic acid group. The N-dialkylamino group, if present on the chain, should be situated at least one carbon atom away, but preferably two carbon atoms away, from the carboxylic acid group. In addition, the carboxylic acid may also contain chlorine or fluorine substituents said halogen substituents being on a primary or secondary carbon atom. Some examples of these parafiinic type carboxylic acids which may be subjected to electrolysis Will include propionic acid, butyric acid, valeric acid, caproic acid, enanthylic acid, caprylic acid, pelargonic acid, capric acid, undecylic acid, lauric acid, tridecylic acid, tridecanoic acid, myristic acid, pentadecanoic acid, palmitic acid, margaric acid, stearic acid, nondecylic acid, arachidic acid, behenic acid, carnaubic acid, hyenic acid, etc. 4-cyclopentylbutyric acid, -cyclopentylvaleric acid, 6-cyclopentylcaproic acid, 7-cyclopentylenanthylic acid, 8-cyclopentylcaprylic acid, 8-cyclohexylcapyrylic acid, 9-cyclohexylpelagonic acid, -cyclohexylcapric acid, 3-methoxypropionic acid, 2-methoxypropionic acid, 3-methoxybutyric acid, Z-methoxybutyric acid, 4-methoxybutyric acid, 5- methoxyvaleric acid, 6-methoxycaproic acid, 7-methoxyenanthylic acid, S-methoxycaprylic acid, 9-methoxypelargonic acid, IO-methoxycapric acid, 4-ethoxybutyric acid, 5-ethoxyvaleric acid, 6-ethoxycaproic acid, 7-ethoxy-enanthylic acid, S-ethoxycaprylic acid, 9-ethoxypelargonic acid, lO-ethoxycapric acid, 4-propoxybutyric acid, 5-propoxyvaleric acid, 6-propoxycaproic acid, 7-propoxyenanthylic acid, 8-propoxycaprylic acid, 9-propoxypelargonic acid, IO-propoxy-capric acid, 2-chloropropionic acid, 3-chloropropoxycapric acid, 2-chloropropionic acid, 2,3,3-chloropropionic acid, 2-chlorobutyric acid, Z-chlorovaleric acid, 2-chlorocaproic acid, 2-chlorolauric acid, 2-chloropalmitic acid, 2-chlorostearic acid, 2-fluoropropionic acid, Z-fiuorobutyric acid, 2-fluorovaleric acid, 2-fluorocaproic acid, 2- fluorolauric acid, 2-fiuoropalmitic acid, 2-fluorostearic acid, etc. If a substituted acid is utilized as the starting material, the substitutent may be located in any position farther than carbon atom number two, with at least one of the valences of carbon atom number three containing a hydrogen atom, and carbon atom number two free of any sterically hindering group. Therefore, it is pr ferred that carbon atom number two is substantially free of any substituents, the remaining carbon atoms then being substituted by alkyl, alkoxy, cycloalkyl, N-dialkylamino, phen l, halogen atoms such as fluorine and chlorine or any combination of these substituents. It is to be understood that the aforementioned carboxylic acids are only representative of the type of acids which may be treated with electrolysis, and that the present invention is not necessarily limited thereto.

The electrolysis, as hereinbefore set forth, is effected in the presence of organic solvents and an alkaline medium. The solvents which are utilized in this process are those which possess high polarity and a high dielectric constant. In addition, the solvents should also possess good solubility for the alkaline medium. Some specific examples of the solvents which may be utilized include the lower molecular Weight alcohols such as methanol, ethanol, n-propanol, n-butanol, etc. as well as diemthyl sulfoxide; glycols such as ethyl glycol, diethylene glycol, propylene glycol, etc.; ethers such as the monomethyl glycol ether, dimethyl glycol ether, etc.; tetrahydrofuran, dioxane, etc. The alkalinity of the medium in which the electrolysis is effected is provided for by alkali metal and alkaline earth metal hydroxides such as potassium hydroxide, sodium hydroxide, lithium hydroxide, rubidium hydroxide, cesium hydroxide. Less preferably calcium hydroxide, magnesium hydroxide, strontium hydroxide, sodium-ptoluenesulfonic acid, potassium-p-toluenesulfonic acid, sodium benzenesulfonic acid, potassium benzene sulfonic acid, corresponding xylyl sulfonic acid salts etc., may also be used. It is also contemplated within the scope of this invention that salts may be used, although not necessarily with equivalent results, said salts including sodium carbonate, potassium carbonate, lithium carbonate, calcium carbonate, etc.

The eletrolysis conditions under which the process of this invention is effected will include temperatures in the range of from ambient up to about 200 C. or more and a pressure ranging from atmospheric up to about 100 atmospheres or more. When utilizing temperatures in the upper portion of the temperature range where the operating tempertaure of the process is above the boiling point of the solvents which are used, it will the necessary to utilize superatmospheric pressures in order that the reaction will be effected in a liquid phase. When superatmospheric pressures are required the necessary pressure will be obtained by utilzing an inert gas such as nitrogen in the reaction vessel. It is to be understood that specific process conditions of temperature and pressure may vary with the different cell structures, with the ratio of the volume of the catholyte to the surface area of the cathode, the ratio of volume of anolyte to the surface area of the anode, etc. Also, the amount of current which is used to efiect the electrolysis may also vary, said current ranging from about 0.5 amperes per square decimeter up to about 40 amperes per square decimeter of cathode area. The time during which the electrolysis or conversion of the acid to the olefin will take place in a range from about 2.5 up to about 10 hours or more in duration.

The electrolysis cell in which the reaction of this invention may be effected may be of any suitable structure known in the art. For example, the cell may be made of glass and will contain electrodes comprising platinum, the solution being stirred by means of a Teflon encased magnetic stirrer. In addition, the anolyte is separated from the catholyte by a semi-porous membrane; these separation means being made of any material known in the art and will include sintered glass, membranes made of synthetic materials such as synthetic cellulose membranes or membranes made of polystyrene sulfonate which is crosslinked with divinyl benzene. In addition, other membranes which may be used include felted asbestos or porous alumina which is in a low micron range. The anolyte will comprise the paraffinic type acid of the kind hereinbefore set forth in greater detail in an aqueous alkaline medium which also contains the solvent. The copper catalyst is added to the anolyte and the current is thereafter charged to the cell. -After a predetermined amount of current, in a range of from about 0.100 up to about 0.25 faraday, has been charged, the electrolysis is allowed to proceed for the aforementioned period of time. At the end of this time, the reaction product is recovered and the desired product comprising the olefinic hydrocarbon is recovered by conventional means which include separation, filtration and fractional distillation.

The following examples are given to illustrate the process of the present invention which, however, are not intended to limit the generally broad scope of the present invention in strict accordance therewith.

EXAMPLE I In this example an electrolytic cell was constructed of glass using a water jacket as a means of applying heat to the cell. The electrodes comprised platinum and the compartments of the cell were divided by a synthetic cellulose semipermeable membrane. The area of the platinum anode was square centimeters and the area of the platinum cathode was 4 square centimeters. A solution of 0.3 mole of n-caprylic acid in an aqueous methanol solution containing 8.4 g. of potassium hydroxide was placed in the anode compartment of the cell and the cell was then heated to a temperature of 50 C. Following this 5 g. of cupric acetate was added to the anolyte and a current of 1.0 amp was charged thereto. After 0.145 faraday of current had been charged during a period of about 4 hours, the electric charge was discontinued. The caustic insoluble product was analyzed by means of a gas liquid chromatograph. The product distribution showed a ratio of 9.2:1 of l-heptene to heptane. It was unexpectedly discovered that the conversion to olefins consisted of all a-olefins in contradistinction to prior art methods which usually gave a mixture of about 50% u-olefins and about 50% B-olefins.

EXAMPLE II In this example an electrolytic cell comprising glass tubes containing platinum electrodes, the components of said cell being divided by a synthetic cellulose membrane contains an aqueous methyl alcohol anolyte. To this anolyte is added 0.3 mole of capric acid, 5 g. of cupric sulfate and 8 g. of potassium hydroxide. The cell is heated to a temperature of 50 C. and 1 amp of current is passed through the cell. At the end of about 4 hours the anolyte is recovered and subjected to analysis by means of a gas liquid chromatograph. The analysis will disclose the presence of a major portion of l-nonene with a very minor portion of 2-nonene being present.

EXAMPLE III A electrolytic cell similar in construction to that described in Example I above containing a platinum anode and a platinum cathode is placed in a water jacket and heated to a temperature of about 50 C. The anolyte which is placed in the anode compartment of the cell will comprise 0.3 mole of caproic acid dissolved in an aqueous methanol solution containing sodium hydroxide to make the solution alkali and a soluble metal salt catalyst comprising cupric benzoate. A current of 1 ampere is passed through the cell for a period of about 4 hours. At the end of this time the current is discontinued and the anolyte is recovered. After separation from the aqueous layer and the solvent, the organic layer which remains is subjected to analysis by means of a gas liquid chromatograph, there being recovered a major portion of l-pentene.

EXAMPLE IV In this example an electrolysis cell similar in nature to that described in the above examples in which the anode compartment and cathode compartment of the cell are separated by a synthetic cellulose membrane has added to the anolyte an aqueous ethanol solution of valeric acid, said solution containing potassium hydroxide to make the solution alkaline and cupric acetate as the soluble metal salt catalyst. The cell is heated to a temperature of about 75 C. and maintained thereat for a period of about 4 hours while passing a current of 1 ampere through the cell. At the end of this time the anolyte is recovered and subjected to separation means whereby the desired organic layer is separated from the aqueous layer and the solvent. Analysis of this layer will disclose the presence of a major portion of l-butene.

EXAMPLE V An aqueous ethanol solution containing lauric' acid which its made alkaline by the addition of sodium hydroxide and which contains cupric acetate as the catalyst therefore is placed in an electrolysis cell similar in nature to those hereinbefore set forth. The cell is heated to a temperature of about 100 C. and maintained thereat for a period of about 4 hours while passing current of 1.2 amperes through the cell. At the end of this time the cell is allowed to return to room temperature and the anolyte is recovered. The anolyte is subjected to conventional separation means whereby the desired organic product is separated from the aqueous layer and the solvent. Analysis of this organic layer by means of a gas liquid chromatograph will disclose the major portion of l-undecene.

We claim as our invention:

1. A process for the preparation of an rat-olefinic hydrocarbon which comprises subjecting a paraffinic type carboxylic acid containing from 3 to about 50 carbon atoms and having at least 3 carbon atoms in a straight chain to electrolysis in an aqueous alkali-organic solvent medium in the presence of a bivalent copper salt which is soluble in said medium and is capable of free radical oxidation, and recovering the resultant tar-olefinic hydrocarbon.

2. The process as set forth in claim 1, further characterized in that said electrolysis is effected at a tempera ture in the range of from about ambient to about 200 C. and at a pressure in the range of from about atmospheric to about 100 atmospheres.

3. The process as set forth in claim 1, further characterized in that said copper salt is cupric acetate.

4. The process as set forth in claim 1, further characterized in that said copper salt is cupric sulfate.

5. The process as set forth in claim 1, further characterized in that said copper salt is cupric benzoate.

6. The process as set forth in claim 1, further characterized in that said carboxylic acid is caprylic acid and said olefinic hydrocarbon is l-heptene.

7. The process as set forth in claim 1, further characterized in that said carboxylic acid is capric acid and said olefinic hydrocarbon is l-nonene.

8. The process as set forth in claim '1, further characterized in that said carboxylic acid is caproic acid and said olefinic hydrocarbon is l-pentene.

9. The process as set forth in claim 1, further characterized in that said carboxylic acid is valeric acid and said olefinic hydrocarbon is l-butene.

10. The process as set forth in claim 1, further characterized in that said carboxylic acid is lauric acid and said olefinic hydrocarbon is l-undecene.

References Cited UNITED STATES PATENTS 7/1967 Smets et al. 204-59 7/1965 Baizer 20472 US. Cl. X.R. 204 

